1. Field of the Invention
The present invention relates to semi-automatic mechanical transmission systems having automatic shifting in the upper two or more ratios and manual shifting in some or all of the lower ratios and, in particular, to a control to allow an operator to request suspension of automatic upper ratio shifting until the occurrence of a predetermined event, such as movement of the shift lever, depression of the clutch pedal or the like.
2. Description of the Prior Art
Partially automated vehicular transmission systems requiring manual shifting in some or all of the lower ratios and having a control for automated shifting in the upper ratios are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,722,248; 4,850,236; 5,038,627; 5,393,276; 5,393,277; 5,498,195 and 5,795,264, the disclosures of which are incorporated herein by reference.
Splitter and combined range and splitter-type compound vehicular transmissions requiring manual splitter shifting are well known in the prior art, as may be seen by reference to U.S. Pat. Nos. 3,799,002; 4,754,665; 4,974,468; 5,000,060; 5,370,013 and 5,390,561, the disclosures of which are incorporated herein by reference.
Such transmissions are commercially sold by Eaton Corporation under the trademark "Top-2" and by Dana Corporation under the trademark "Automate II."
It is desirable to improve these prior art systems by providing a control which will allow the vehicle operator to request that automatic upper ratio shifting be suspended, and the transmission be retained in the currently engaged upper ratio, until the occurrence of a predetermined event. Preferably, this control feature will be provided without the necessity of additional control members.